I upgraded to 7.30 and started having problems. When I plugged in my Nook it show up in Calibre just fine however when I tried to transfer a book it said there was no device attached. I also noticed that the Calibre server was not running and would not start. I upgraded to 7.31 and the same conditions existed. I uninstalled 7.31, rebooted my system and installed 7.29 and everything works fine. I can transfer books and my Calibre server is running.